1. Technical Field of the Invention
The present invention relates to a method of transmitting transparent data on a radio system, and more particularly to a method of transmitting transparent data requiring a real-time nature, as in audio or video streaming data, by means of a radio system, such as of Bluetooth (Bluetooth SIG Inc. trademark, United States).
2. Description of the Related Art
Recently, there are a diversity of applications for communication requiring such real-time natures as to sequentially transmit a set amount of data within a constant time period by means of packet transmission, as in audio or video streaming data.
The need for supporting such application on the radio system is increasing. In radio transmission, packet missing is unavoidable due to on-transmission-line errors because of readily suffering from the effect of fading or external noise. Even on such an application as requiring real-time natures, where specialized for audio transmission, the effect of on-transmission-line errors can be reduced by adopting an audio coding scheme, or the corresponding control scheme, for the human eye to less perceive an error through the function of audio CODEC even upon an occurrence of packet missing due to on-transmission-line error.
However, due to the diversified applications, there is a difficulty in specifying the application concerned, thus making it difficult to reduce the influence of on-transmission errors. Consequently, there is a requisite need for a transmission scheme capable of reducing on-transmission-line errors and securing real-time nature. Furthermore, on a packet-transmission-based radio system, other services than those of streaming data are to be offered concurrently. Considerations must be given to the compatibility with those services.
FIGS. 1A to 1C are figures showing transmission schemes as to transparent data.
FIG. 1A shows that, taking an on-transmission-line slot interval as T, where there is a need to process data in a certain amount (e.g. 4M) with a constant period of transparent-data transmission (e.g. 16T), the data in an amount 4M is sent as one packet on the first slot in the period. When a transmission error occurs within the first slot, resend can be subsequently effected by use of a resend-reserve slot assigned for resending the transparent data until transmission is normally done. The slots successful in normal transmission are used for transferring data of another application, including resend-reserve slots.
The transmission scheme of FIG. 1A has a feature as follows.
For the transmission service of transparent data, the information to be sent on one packet is in an increased amount. This increases the efficiency of transfer per packet thus enabling to increase the total efficiency of slot use. Meanwhile, because of transferring information in greater amount in a brief time, there is a difficulty or impossibility in adding redundant bits such as error correction codes. For this reason, where the quality of transmission line is worse, there arises a fear that data transfer is not available because of transmission errors.
For the total service of data transfer to offer, the efficiency of slot use can be raised in a state that transmission line quality is well and resend is not raised frequently. Meanwhile, because a smaller number of slots are to be transferred in a constant time period, there is not always a need to provide resend occasions in the same number of times as those with a shorter period of packet transmission. By reducing the resend occasions, the total efficiency of transfer can be raised including other services.
FIG. 1B shows that, taking an on-transmission-line slot interval as T similarly, where there is a need to process data in a certain amount (e.g. 4M) in every period of constant transparent-data transmission (e.g. 16T), the period of transparent-data transmission is divided into a plurality of time periods (e.g. four time periods wherein one time period is given 4T), to send data in an amount M as one packet on the first slot of each divisional period. When a transmission error occurs in the first slot, resend can be subsequently effected by use of a resend-reserve slot until transmission is normally done. The slots successful in normal transmission are used for transferring data of another application, including resend-reserve slots.
FIG. 1C shows that, taking an on-transmission-line slot interval as T similarly, where there is a need to process data in a certain amount (e.g. 4M) in every period of constant transparent-data transmission (e.g. 16T), the data in an amount 4M is divided to produce four packets each having a data amount M, to sequentially send the slots starting from the first one in the constant time period. When a transmission error occurs, resend can be effected by use of a resend-reserve slot until transmission is normally done. The slots, successful in normal transmission as to all the four packets, are used for data transfer for another application.
The transmission schemes of FIGS. 1B and 1C have features as follows.
For the transmission service as to transparent data, the information to be sent on one packet is in a reduced amount. This makes it possible to add redundant bits in greater amount correspondingly, thus realizing an effective error correction. Meanwhile, because of addition of overhead data besides the data to be used on the applications, the efficiency of packet transfer per packet is reduced and hence the total efficiency of slot use becomes low.
For the total service of data transfer to offer, the slots in the greater number are used for transmission of transparent data. This reduces the slots to be assigned for other services, thus reducing the efficiency of transfer.
Non-patent Document 1, “Specification of the Bluetooth System” vol 2, ver 1.2, Nov. 5, 2003, p 151-152 (United States), regulates a transmission scheme of extended SCO (Synchronous Connection Oriented) transparent data in Bluetooth.
As noted before, the transmission schemes of transparent data in FIGS. 1A to 1C involve merits and demerits. Particularly where using a transmission line not stable in transmission quality as in the radio system, it is not proper to employ any one scheme fixedly. However, Non-patent Document 1 does not regulate a transmission scheme for providing an efficient transmission line to a transmission line not stable in transmission quality.